1. Field of the Invention The disclosure relates to pile oil field equipment, and particularly for oil field equipment designed to drilling and production of hydrocarbons from oil and gas wells.
2. Description of Related Art
It is a common practice when drilling and producing an oil or gas well to insert casing into the drilled hole and mount a wellhead assembly above ground to the casing. The wellhead assembly is a series of stacked devices, each having an internal bore aligned with the casing. For example, a casing head is mounted to the casing, followed by a tubing head with a packoff bushing disposed therein, followed by a blowout preventer and other devices. Production tubing is generally suspended from the wellhead assembly during normal operations to conduct production fluids, such as oil and natural gas and other fluids, to the surface and out of the well to production facilities for processing. As the well is drilled deeper, the well pressure is expected to increase. Consequently, the pressure rating of the wellhead stack needs to increase, as do the element sizes and lengths. Seals are used between the casing and tubing hangers and other wellhead devices along the surfaces to which they interact.
Some wells require additional steps to enhance production or “stimulate” the well through a technique known as “fracturing.” The process of fracturing generally pumps high pressure fluids down the casing and into the production strata to expand the porosity and interstitial spaces of the strata and allow production fluids to flow more easily therethrough. However, the fracturing process can involve abrasive fluids that can harm seals and other portions of the devices in the wellhead assembly. The fracturing pressure can also exceed the production pressure ratings of the wellhead assembly. Thus, it is common to use a fracturing isolation sleeve that slides into the internal bore of the wellhead assembly. An isolation sleeve with seals on its outside diameter at least partially isolates the wellhead devices, such as a tubing head with its outlets and other ports, from high fracturing pressures and fluids. To facilitate the fracturing process, generally a fracturing adapter is added to the wellhead assembly stack of devices above the tubing head. The isolation sleeve can be slipped at least partially into the fracturing adapter, coupled to the fracturing adapter, and sealably engaged with one or more devices of the wellhead assembly. The fracturing fluid can flow through an internal bore of the isolation sleeve while the sleeve at least partially isolates and protects the internal bore of the wellhead assembly.
It has been quite common for years to use lock down pins extending through the wall of the wellhead assembly to support devices within the internal bore of the wellhead assembly, such as casing hangers, tubing hangers, and other internal devices which are commonly used in the oil field tooling. Known fracturing sleeves are usually held in place by a set of such lock down pins. Also, known isolation sleeves have an inner diameter that is equal to or greater than the casing or other tubular element that is in place during the fracturing process. That relative inner diameter allows equipment sized up to the full bore of the tubular element to pass through the isolation sleeve at various stages of the fracturing process.
Installing the isolation sleeve is generally in a downward direction by inserting the sleeve through one or more wellhead devices into the fracturing adapter and/or other devices of the wellhead assembly. However, removal in the reverse upward direction can be difficult. After a fracturing operation, the sleeve can become hard to remove manually due to the extreme pressures and can cause the sleeve to become lodged in position. At times, hydraulic pressure is applied from the outlets back into a sealed annulus between the tubing head and the outer diameter of the isolation sleeve to cause the isolation sleeve to be forced partially upward and push the sleeve partially out of the fracturing adapter and/or tubing head, or other devices of the wellhead assembly. However, as soon as the seals extend beyond the sealed internal bore, the pressure dissipates and can longer be used as a medium to continue pushing out the isolation sleeve. Thus, the force to remove the remainder of the isolation sleeve can become a challenge when a drilling rig is not present when the sleeve has to be removed manually.
The complexities are extended when different wells have different wellhead assembly stack heights due to different pressure ratings. Different isolation sleeves even of the same diameter are sometimes used at well sites to accommodate the different stack heights due to the different pressure ratings of the wellhead assembly.
Therefore, there remains a need to provide an improved system and method that can reliably remove an isolation sleeve and is adapted to accommodate various spacings of devices used in the wellhead assembly.